The present invention relates to multi-piece solid golf balls having a solid core, at least one intermediate layer, and a cover.
Various improvements are being made in the compounding of golf ball materials so as to confer golf balls with an excellent rebound. But more is desired of a golf ball than just an excellent rebound; a range of other qualities, including a soft feel on impact and outstanding durability, are also desired as well. A major concern is how to provide to a high degree these different properties in a single golf ball. The ability to maintain a high rebound over a broad range in temperature is also important as one of these various properties desired in a golf ball.
Related art in which silicone components are incorporated so as to provide golf balls which are easy to mold and have both a stable flexibility and a high rebound over a broad temperature range includes golf balls in which a part of the ball is made of a composition containing at least one powder selected from among silicone rubber powders, silicon resin powders and composites thereof (JP-A 2001-170213, JP-A 2002-331046). However, there is room for further improvement in terms of obtaining golf balls that exhibit a stable rebound over a broad temperature range, yet also have a higher rebound. Additional art involving the incorporation of silicone powder within golf ball materials has also been disclosed (JP-A 2001-353233), but such art too falls short of satisfying the desires of golfers.
In addition to the above, other art that calls for compounding silicone components in golf ball-forming materials include the efforts, described in, for example, JP-A 60-258236, JP-A 61-258844 and JP-A 8-243191, to blend millable silicone rubber into a polybutadiene rubber or a cover layer resin, then to use a peroxide to effect crosslinking. However, it is not easy to microdisperse silicone rubber in polybutadiene rubber or to microdisperse polybutadiene rubber in silicone rubber. In the interest of improving certain properties, such as flow (injection moldability) during golf ball formation and durability of the golf ball, which are intimately associated with the morphology of the blended state between these two components, there exists a need for a way to achieve a better state of dispersion between the two components.
To address the desires of professional golfers and skilled amateurs, JP-A 7-24085 discloses a solid golf ball having a three-piece construction which is hard on the interior and soft at the exterior. JP-A 10-151226 describes such a golf ball which is also endowed with improved spin, flight characteristics and durability. Yet, even with these improvements, the golf balls often fall short of what is desired.
Multi-piece solid golf balls are also described in, for example, JP-A 2001-149505, JP-A 2001-149506, JP-A 2001-149507, JP-A 2002-315848, JP-A 2003-190330 and U.S. Pat. No. 6,659,889. However, further improvement in such balls continues to be desired.